The present invention relates to a technique for reliably protecting data being generated by a user on an apparatus including an operating system having a simplified user switching function.
Among multiuser and multitasking-capable operating systems used in computer systems, an operating system having a simplified user switching function (for example Windows XP: trademark of Microsoft Corp.) is known which provides a convenient function (function on a local computer) when a single computer is used by a plurality of people. Specifically, without requiring log-off by a user, the operating system allows switching to another user while in a log-on state after personal identification through input of a password or the like. The operating system therefore provides an advantage in that when the single computer is shared by a family, for example, the same application can be used while each member of the family changes the desktop (working space on a computer screen).
When a user of a conventional apparatus executes a desired application (for example word processing or image processing software) on an operating system (hereinafter referred to simply as an “OS”) having the simplified user switching function, data of the application of a user being logged on to the computer but not active (previous user when the desktop is switched to that of the other user) may be lost. Therefore, the data is not protected adequately.
Suppose that an OS having the simplified user switching function is installed in a single computer, and that two or more users are registered with the computer, for example.
Suppose that a user A is doing work using an application program (described as “P”), and that concentrating too much on the work and forgetting to store data, the user A has not yet stored data in a file. When the user A leaves the computer in that state and switching from the user to another user B is performed to use an application, the following procedure is generally used.                1. Operation of switching to the user B        2. Switching to a via screen (“Welcome Screen” to be described later)        3. Logging on of the user B        4. Starting up the application by the user B        
At this time, the user A is in a logged-on state (process of the application and the like is not ended and is being performed), but the user A is not active (∵ the desktop is changed to that of the user B). When the user B is to perform a shutdown operation to turn off the computer, a message from the OS to the following effect is displayed on the screen, for example.
“Another person is logged on to this computer. Shutting down the OS may cause data of the person to be lost. Proceed with the shutdown? [Yes] [No]”
This is display content of a dialog box appearing on the screen to ask the user B for a positive or negative answer. When [Yes] is chosen, the possibility of loss of the data of the application program P started up by the user A is increased.
The user B (currently active user) can store data of the application started up himself/herself anytime before performing the shutdown operation. However, when the user B looks at the message before the shutdown operation and fortunately realizes that the data of the application program P started up the user A needs to be stored, the user B needs to ask the user A a password, perform user switching to the user A, and then store the data of the application program P on behalf of the user A (there is a problem in terms of security) The only alternative for the user B is to find the user A, bring the user A to the computer, and perform user switching to the user A so that the user A himself/herself stores the data.
Of course, some applications have a function of automatically storing data at fixed time intervals. For example, when a timer operated at predetermined time intervals or time intervals specified by the user is used to automatically store a backup file at appropriate times, it is possible to obtain data up to a point in time when the file was stored. However, when the automatic storing function is not set or the time intervals of the timer are set long, for example, the data cannot be stored reliably.
At the time of a shutdown, a message notifying the shutdown is issued from the OS to all the applications of all the users. Therefore, when a function of storing data within the application of an inactive user is activated as it is, the application can automatically store data when receiving the message. However, when there is a large amount of data to be stored, or the shutdown time is very short (a forced shutdown by a user, power cutoff or the like), for example, the shutdown may be performed before the storing of the data is completed.
Such problems always present a danger of losing the data of an inactive user, and thus make the simplified user switching function less easy to use.